DESCRIPTION (Investigator's Abstract): The purpose of the proposed research is to compare recent memory functions in preclinical individuals at the earliest stages of Alzheimer's disease (AD) to age and eduction matched controls. Disturbed memory for recent events is a prominent symptom of Alzheimer's disease. On neuropsychological testing, significant impairments in recall and recognition (explicit memory) are particularly apparent early in the disease. In contrast, other aspects of recent memory not dependent on conscious recall (implicit memory) are relatively spared. Dissociation in memory functions such as this may prove useful in distinguishing normal elderly individuals from those with early AD. However, whether memory change forms an early signature of impending AD remains undetermined and difficult to study as affected individuals without clear symptoms do not generally reach medical attention. To optimize the early identification of AD, this project prospectively studies a unique population at a higher risk of developing the disorder by virtue of a strong family history of confirmed AD. Subjects will be followed longitudinally with a series of traditional neuropsychological tests and with experimental memory measures. Three experimental memory paradigms will be used to determine recall, recognition, forgetting rates, recently judgement and implicit priming in order to assess whether dissociations in recent memory functions as seen in AD patients are predictive of incipient disease. Several major questions will be addressed:1) Do persons at risk for AD differ as a group from age and education matched controls in baseline measures of recent memory function at the beginning of the proposed longitudinal study? 2) Are persons with the poorest memory performance at baseline at greater risk for developing AD dementia? 3) Is there a greater decline in recent memory functions in persons at risk for AD than in age and education matched controls, and 4) Is there a characteristic profile of memory outcomes which reliably predicts those at-risk individuals who develop AD over the course of study?